Common path scanning heterodyne optical profilometer for absolute phase measurement

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Abstract
A scanning optical profilometer is described which overcomes some of the limitations of existing interferometric profilometers. Two laser beams are incident on the sample ensuring common path operation. One beam forms a tightly focused sample probe spot and the other remains collimated, acting as a large-area, common path reference beam. Our configuration allows the relative size of the two beams to be varied both arbitrarily and independently, thus guaranteeing an accurate absolute phase measurement. Preliminary results demonstrating the operation of the system are presented.